Distinguishing Dilute and Concentrated Nitric Acid: Chemical Methods
How do you distinguish dilute nitric acid and concentrated nitric acid using chemical methods?
Answer:
I have two methods to distinguish between concentrated and dilute nitric acid:
Method 1: Using magnesium/manganese.
Mg + 2HNO₃ (1%) → Mg(NO₃) + H₂ - very very dilute
Mg + 4HNO₃ → Mg(NO₃) + 2H₂O + 2NO₂ - concentrated
In the first reaction of magnesium with concentrated nitric acid, hydrogen is evolved.
In the second reaction of magnesium with very very dilute nitric acid, water is evolved.
Using the respective tests for hydrogen and water, we can distinguish them.
Method 2: Using iron.
3 Fe + 8HNO₃ → 3Fe(NO₃)₂ + 4H₂O + 2NO - dilute
Fe + 6HNO₃ → Fe(NO₃)₃ + 3H₂O + 3NO₂ - concentrated
In the first case of method 2, Fe(NO₃)₂ ⇆ Fe²⁺ + (NO₃) ⁻ Iron with valency 2+ is formed.
In the second case of method 2, Fe(NO₃)₃ ⇄ Fe³⁺ + (NO₃) ⁻ Iron with valency 3+ is formed.
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Distinguishing Between Dilute and Concentrated Nitric Acid
When it comes to distinguishing between dilute and concentrated nitric acid using chemical methods, we have two effective approaches: using magnesium/manganese or iron.
Method 1 involves the reaction of magnesium with nitric acid. When magnesium reacts with very very dilute nitric acid, water is evolved, while in concentrated nitric acid, hydrogen is evolved. This difference in reaction products helps in identifying the concentration of the acid.
Method 2 utilizes iron to differentiate between dilute and concentrated nitric acid. The formation of iron with different valencies (Fe²⁺ and Fe³⁺) in the reactions indicates the concentration of the nitric acid being tested.
By conducting these chemical tests using magnesium/manganese or iron, one can accurately determine whether the nitric acid in question is dilute or concentrated.
Detail Explanation:
When conducting chemical tests to distinguish between dilute and concentrated nitric acid, it is crucial to understand the specific reactions that occur with different substances, such as magnesium, manganese, and iron.
In Method 1, the reactions of magnesium with nitric acid showcase the differences between dilute and concentrated solutions based on the evolution of either water or hydrogen. This approach is effective in providing a visual indicator of the acid's concentration.
On the other hand, Method 2 involves using iron to observe the formation of iron with varying valencies, indicating the concentration levels of the nitric acid being tested. The valency changes in iron serve as a distinctive marker for dilute or concentrated nitric acid.
By carefully analyzing the reaction products and understanding the underlying chemistry principles, one can accurately determine the concentration of nitric acid through these chemical methods. These methods offer a practical and reliable way to differentiate between dilute and concentrated nitric acid in various laboratory settings.